private void UseStartup([DynamicallyAccessedMembers(StartupLinkerOptions.Accessibility)] Type startupType, HostBuilderContext context, IServiceCollection services, object?instance = null)
{
var webHostBuilderContext = GetWebHostBuilderContext(context);
var webHostOptions = (WebHostOptions)context.Properties[typeof(WebHostOptions)];
ExceptionDispatchInfo?startupError = null;
ConfigureBuilder? configureBuilder = null;
try
{
// We cannot support methods that return IServiceProvider as that is terminal and we need ConfigureServices to compose
if (typeof(IStartup).IsAssignableFrom(startupType))
{
throw new NotSupportedException($"{typeof(IStartup)} isn't supported");
}
if (StartupLoader.HasConfigureServicesIServiceProviderDelegate(startupType, context.HostingEnvironment.EnvironmentName))
{
throw new NotSupportedException($"ConfigureServices returning an {typeof(IServiceProvider)} isn't supported.");
}
instance ??= ActivatorUtilities.CreateInstance(new HostServiceProvider(webHostBuilderContext), startupType);
context.Properties[_startupKey] = instance;
// Startup.ConfigureServices
var configureServicesBuilder = StartupLoader.FindConfigureServicesDelegate(startupType, context.HostingEnvironment.EnvironmentName);
var configureServices = configureServicesBuilder.Build(instance);
configureServices(services);
// REVIEW: We're doing this in the callback so that we have access to the hosting environment
// Startup.ConfigureContainer
var configureContainerBuilder = StartupLoader.FindConfigureContainerDelegate(startupType, context.HostingEnvironment.EnvironmentName);
if (configureContainerBuilder.MethodInfo != null)
{
var containerType = configureContainerBuilder.GetContainerType();
// Store the builder in the property bag
_builder.Properties[typeof(ConfigureContainerBuilder)] = configureContainerBuilder;
var actionType = typeof(Action <,>).MakeGenericType(typeof(HostBuilderContext), containerType);
// Get the private ConfigureContainer method on this type then close over the container type
var configureCallback = typeof(GenericWebHostBuilder).GetMethod(nameof(ConfigureContainerImpl), BindingFlags.NonPublic | BindingFlags.Instance) !
.MakeGenericMethod(containerType)
.CreateDelegate(actionType, this);
// _builder.ConfigureContainer<T>(ConfigureContainer);
typeof(IHostBuilder).GetMethod(nameof(IHostBuilder.ConfigureContainer)) !
.MakeGenericMethod(containerType)
.InvokeWithoutWrappingExceptions(_builder, new object[] { configureCallback });
}
// Resolve Configure after calling ConfigureServices and ConfigureContainer
configureBuilder = StartupLoader.FindConfigureDelegate(startupType, context.HostingEnvironment.EnvironmentName);
}
catch (Exception ex) when(webHostOptions.CaptureStartupErrors)
{
startupError = ExceptionDispatchInfo.Capture(ex);
}
// Startup.Configure
services.Configure <GenericWebHostServiceOptions>(options =>
{
options.ConfigureApplication = app =>
{
// Throw if there was any errors initializing startup
startupError?.Throw();
// Execute Startup.Configure
if (instance != null && configureBuilder != null)
{
configureBuilder.Build(instance)(app);
}
};
});
}